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kinetics
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An investigation on the calcination kinetics of zinc carbonate hydroxide and Calsimin zinc carbonate concentrate
, Article Chemical Engineering Journal ; Volume 121, Issue 2-3 , 2006 , Pages 79-84 ; 13858947 (ISSN) ; Halali, M ; Sharif University of Technology
2006
Abstract
In this study the thermal calcination of two materials, high purity zinc carbonate hydroxide and the Calsimin zinc carbonate concentrate have been investigated. Isothermal studies have been performed on samples at different temperatures and times. Non-isothermal analysis has been carried out by TGA and DSC. It has been found that the calcination behaviour of both materials corresponds to the shrinking core model. The activation energy for the calcination of zinc carbonate hydroxide is found to be 88.7 kJ/mol, and that for the Calsimin sample is 97.3 kJ/mol. © 2006 Elsevier B.V. All rights reserved
Investigating the effect of mixing layer rheology on granular flow over entrainable beds using SPH method
, Article Computers and Geosciences ; Volume 155 , 2021 ; 00983004 (ISSN) ; Manzari, M. T ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
This paper numerically studies the interaction of a flowing granular material with an entrainable granular bed, while materials are mixed at the interface of two materials. The rheological behavior of this granular mixture is characterized by a generalized viscoplastic model that includes local volume fraction of materials as well as their physical properties, i.e. size, density, and friction angle. Additionally, the effect of the dynamics of entrained bed-type particles on the rheology of the granular mixture is considered. The governing equations of the flow are discretized using the Incompressible Smoothed Particle Hydrodynamics (SPH) method in which mixing of particles can be...
Spinel H4Ti5O12 nanotubes for Li recovery from aqueous solutions: Thermodynamics and kinetics study
, Article Journal of Environmental Chemical Engineering ; Volume 9, Issue 1 , 2021 ; 22133437 (ISSN) ; Ghasemi, S ; Askari, M ; Khosravi, A ; Hasan Zadeh, A ; Alamolhoda, A. A ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
In this study, H4Ti5O12 nanotubes have been prepared as Li+ adsorbent by acid treatment of Li4Ti5O12 nanotubes. Li4Ti5O12 nanotubes were synthesized via a hydrothermal method in which TiO2(B) nanNotubes were used as a precursor. The prepared Li-ion sieve showed a significant high ion-exchange capacity (160.6 mgg−1) for lithium ions due to its large specific surface area of 115.4 m2 g-1 compared to the other related studies. The kinetics and isotherm investigation revealed that the pseudo-second-order equation well described the adsorption kinetics, and the Langmuir model well fitted the isotherm data. Furthermore, the low value of adsorption energy obtained from the Dubinin-Radushkevitch...
Modeling of Side Reactions in Propane Dehydrogenation Over Pt-Sn/γ-Al2O3 Catalyst
, M.Sc. Thesis Sharif University of Technology ; Khorasheh, Farhad (Supervisor)
Abstract
The kinetics of side reactions in dehydrogenation of propane over a supported platinum catalyst modified by tin was investigated. Catalytic dehydrogenation over a commercial Pt-Sn/γ-Al2O3 was carried out in a laboratory-scale plug-flow reactor at 580 to 620oC under atmospheric pressure. Several kinetic models derived from different reaction mechanisms were tested using experimental data obtained over a range of reaction conditions. It was found that the kinetics of the main dehydrogenation reaction was best described in terms of a Langmuir-Hinshelwood mechanism where adsorption of propane was the rate controlling step. Simple power low rate expressions were used to express the kinetics of...
Kinetics and Mechanism Study of Chemical Pollutant Adsorption Using Organic Ligands Modified Nano-adsorbents
, M.Sc. Thesis Sharif University of Technology ; Golami, Mohammad Reza (Supervisor)
Abstract
Among various methods for purifying water from dyes, adsorption takes advantage of simplicity, high efficiency, no secondary-pollution, and inexpensiveness. In this project Halloysite nanoparticles were applied to prepare a series of modified polyAcrylamide- quince seed gum hydrogels (QS/PAAm/Haln). The obtained hydrogels demonstrated improved efficiency as adsorbent in removing methylene blue (MB) from aqueous media. The structure of the prepared hydrogel nanocomposites were identified by X-ray diffraction, Brunauer-Emmett-Teller surface area analysis, Fourier-transform infrared spectroscopy, scanning electron microscope and energy-dispersive X-ray spectroscopy. Kinetics, thermodynamic,...
In-situ nitrate remediation using nano iron/nickel particles
, Article Environment Protection Engineering ; Vol. 40, issue. 3 , 2014 , p. 75-86 ; Vossoughi, M ; Shamsai, A ; Sharif University of Technology
Abstract
Originally, the application of nano zero valent iron/nickel (nZVI/Ni) particles for nitrate removal in porous media was studied. nZVI/Ni was prepared and employed in batch and continuous modes. Based on batch experiments, the reaction kinetics was consistent with the adsorption model by the order of 1-1.5. The variation of the kinetics order depends on pH and nickel content. So that highest reactivity was observed for nZVI with 10% of Ni at pH ≤ 3. Nitrate remediation in a continuous system was mostly influenced by seepage velocity, quantity and freshness of nZVI/Ni and particle size of porous media. In a batch mode, the maximum nitrate removal was 99% while in a continuous mode it did not...
Study on the acetylene hydrogenation process for ethylene production: simulation, modification, and optimization
, Article Chemical Engineering Communications ; Volume 200, Issue 7 , Mar , 2013 , Pages 863-877 ; 00986445 (ISSN) ; Zolfaghari Sharak, A ; Mousavi, S. A ; Bakhtiari Ziabari, F ; Shariati, J ; Azizi, S ; Sharif University of Technology
2013
Abstract
In this study, an industrial acetylene hydrogenation unit is simulated utilizing three available kinetic models. The results are compared against six-day experimental data and the best model is selected. Effects of feed temperature and the amount of injected hydrogen on ethylene selectivity are also studied. According to the simulation results, the unit is not working under its optimum conditions. Furthermore, by reduction of the hydrogen flow rate to 52 kg/h, process selectivity is increased. In addition, a new approach is proposed to modify the hydrogenation process and reduce undesired by-products. In the simulation of the modified process, hydrogenation reactors temperature, hydrogen...
Kinetic Euclidean minimum spanning tree in the plane
, Article Journal of Discrete Algorithms ; Volume 16 , October , 2012 , Pages 2-11 ; 15708667 (ISSN) ; Zarei, A ; Sharif University of Technology
Elsevier
2012
Abstract
This paper presents a kinetic data structure (KDS) for maintenance of the Euclidean minimum spanning tree (EMST) on a set of moving points in 2-dimensional space. For a set of n points moving in the plane we build a KDS of size O(n) in O(nlogn) preprocessing time by which the EMST is maintained efficiently during the motion. This is done by applying the required changes to the combinatorial structure of the EMST which is changed in discrete timestamps. We assume that the motion of the points, i.e. x and y coordinates of the points, are defined by algebraic functions of constant maximum degree. In terms of the KDS performance parameters, our KDS is responsive, local, and compact. The...
A novel approach to find the kinetics of dynamic recovery based on hot flow curves
, Article Materials Science and Engineering A ; Volume 544 , May , 2012 , Pages 88-91 ; 09215093 (ISSN) ; Kazeminezhad, M ; Sharif University of Technology
2012
Abstract
A novel method is proposed in order to find the kinetics of dynamic recovery in the form of Avrami relation using hot flow curves. The relation is derived on the basis of variation of dislocation density with strain. The model is applied on an Al-Mg alloy
Investigating the propagation noise in PWRs via closed-loop neutron-kinetic/thermal-hydraulic noise calculations
, Article Annals of Nuclear Energy ; Volume 80 , 2015 , Pages 101-113 ; 03064549 (ISSN) ; Vosoughi, N ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
Neutron noise induced by propagating thermal-hydraulic disturbances (propagation noise for short) in pressurized water reactors is investigated in this paper. A closed-loop neutron-kinetic/thermal-hydraulic noise simulator (named NOISIM) has been developed, with the capability of modeling the propagation noise in both Western-type and VVER-type pressurized water reactors. The neutron-kinetic/thermal-hydraulic noise equations are on the basis of the first-order perturbation theory. The spatial discretization among the neutron-kinetic noise equations is based on the box-scheme finite difference method (BSFDM) for rectangular-z, triangular-z and hexagonal-z geometries. Furthermore, the finite...
Kinetic modeling of thermal hydrocracking of a paraffinic feedstock
, Article Energy and Fuels ; Volume 30, Issue 4 , 2016 , Pages 3374-3384 ; 08870624 (ISSN) ; Khorasheh, F ; Sharif University of Technology
American Chemical Society
2016
Abstract
A kinetic model based on a mechanistic approach was developed for thermal hydrocracking of a paraffinic feedstock. The hydrocarbon feed was described as a mixture of representative molecules based on structural group analysis (SGA) where information from elemental analysis, H1, and C13-NMR of the feed were used to obtain the average concentration of various structural groups from which representative molecules were constructed. The behavior of the feedstock under reaction conditions was described in terms of the reaction of the individual molecules. The reaction of each of the representative molecules and the corresponding product distribution was based on free radical mechanisms. The...
On the limitations of linear power reactor noise analysis: A point kinetics approach
, Article Annals of Nuclear Energy ; Volume 102 , 2017 , Pages 124-133 ; 03064549 (ISSN) ; Vosoughi, N ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
A novel method is introduced which allows the higher order perturbative solution of a linear operator with a time variant coefficient. This method employs a form of raising and lowering operators which generate higher and lower order harmonics from a given harmonic. The analysis has been applied to the point kinetics equations with a monotone oscillatory reactivity to place bounds on the relative error of the linearization method frequently employed in the power reactor noise techniques. As a result, the maximum permissible reactivity amplitude for a given reactor as a function of frequency has been obtained such that regular power reactor noise methods remain accurate enough. Three...
Kinetic polar diagram
, Article 13th International Computer Society of Iran Computer Conference on Advances in Computer Science and Engineering, CSICC 2008, Kish Island, 9 March 2008 through 11 March 2008 ; Volume 6 CCIS , 2008 , Pages 283-290 ; 18650929 (ISSN); 3540899847 (ISBN); 9783540899846 (ISBN) ; Chitforoush, F ; Yazdandoost, M ; Ghodsi, M ; Sharif University of Technology
2008
Abstract
Polar Diagram [4] is a new locus approach for problems processing angles. The solution to many important problems in Computational Geometry requires some kind of angle processing of the data input. Using the Polar Diagrma as preprocessing, exhaustive searches to find those sites with smallest angle become unnecessary. In this paper, we use the notion of kinetic data structure [1][2] to model the dynamic case of polar diagram, i.e we maintain the polar diagram of a set of continuously moving objects in the scene. We show that our proposed structure meets the main criteria of a good KDS. © 2008 Springer-Verlag
A kinetic study on the electrodeposition of cadmium with the presence of organic agents in sulfate solutions
, Article Materials Chemistry and Physics ; Volume 94, Issue 1 , 2005 , Pages 23-28 ; 02540584 (ISSN) ; Afshar, A ; Ghasemi, H ; Sharif University of Technology
2005
Abstract
The electrodeposition of cadmium is studied by electrochemical techniques with the presence of the organic agents. The cyclic voltammetry results clearly show that the electrodeposition of cadmium is a diffusion-controlled process associated with a typical nucleation process. With addition of the thiourea, 3-Picolin and benzyl alcohol organic agents simultaneously in sulfate solution, the redox potential of cadmium is shifted to more negative potentials. In this case, the current transients reveal an instantaneous nucleation with a typical three-dimensional (3D) growth mechanism, while it shows progressive nucleation mechanism without the ternary-species organic agents. In addition, the...
Nickel Recovery from Spent Catalyst of Reformers
, M.Sc. Thesis Sharif University of Technology ; Halali, Mohammad (Supervisor)
Abstract
In this research, Nickel recovery has been investigated from spent catalyst (NiO/Al2O3) in reformers of direct reduction iron plant (Midrex). Genetic Algorithm method was applied for screening and optimization of the parameters affecting on the Ni dissolution in sulphuric acid by means of Design Expert Software. In accordance with the results, temperature, time, acid concentration and particle size were introduced as the effective parameters on the catalyst leaching. In the next step, the optimization experiments, the optimal parameters were achieved as following: Temperature = 95 C, Acid concentration = 5 Molar, Time = 255 minute, Stirring speed = 600 rpm, Particle size = 50-60 micron and...
Synthesis of Modified Porous Nanostructures and Investigation of Oxidation Reaction Kinetics
, M.Sc. Thesis Sharif University of Technology ; Gholami, Mohammad Reza (Supervisor)
Abstract
In this work ،we used the hydrothermal method for prepared the Bivo4 nano particles. For the best photocatality property these nano particles stabilized on the different basis. This catalysis characterized by UV-vis, XRD, BET, FTIR and SEM. The size of zeolites catalyst were 22 nm and size of Bivo4 were 54 nm and the SEM showed that the BivO4 were sphere. By addition of BiVO4 nano particles to the surface of zeolite, the surface area was increase, but addition of BiVO4 nano particles to surface, the average of holes size decreased and distribution of holes will be monotonous and the surface area increased. In the continue for investigation of photo catalyst activity of nano particle, we used...
An investigation of the oxidative dehydrogenation of propane kinetics over a vanadium-graphene catalyst aiming at minimizing of the COx species
, Article Chemical Engineering Journal ; Vol. 250 , 2014 , Pages 14-24 ; ISSN: 13858947 ; Kazemeini, M ; Khorasheh, F ; Rashidi, A ; Sharif University of Technology
Abstract
Application of the DOE with the ANN in kinetic study of the ODHP was investigated.•The catalyst of vanadium/graphene synthesized through the hydrothermal technique.•The ANN and RSM's simulations were utilized to generate the extra data points.•Power law models and corresponding parameters determined to describe the reactions.•The optimization conducted in order to minimize the COx production. In the current investigation, an application of the design of experiments (DOE) along with the artificial neural networks (ANN) in a kinetic study of oxidative dehydrogenation of propane (ODHP) reaction over a synthesized vanadium-graphene catalyst at 400-500. °C presented aiming at minimizing the CO. x...
Kinetic modeling of oxidative dehydrogenation of propane (ODHP) over a vanadium-graphene catalyst: Application of the DOE and ANN methodologies
, Article Journal of Industrial and Engineering Chemistry ; Vol. 20, issue. 4 , July , 2014 , p. 2236-2247 ; ISSN: 1226086X ; Kazemeini, M ; Khorasheh, F ; Rashidi, A ; Sharif University of Technology
Abstract
In this research the application of design of experiment (DOE) coupled with the artificial neural networks (ANN) in kinetic study of oxidative dehydrogenation of propane (ODHP) over a vanadium-graphene catalyst at 400-500 °C and a method of data collection/fitting for the experiments were presented. The proposed reaction network composed of consecutive and simultaneous reactions with kinetics expressed by simple power law equations involving a total of 20 unknown parameters (10 reaction orders and 5 rate constants each expressed in terms of a pre-exponential factors and activation energies) determined through non-linear regression analysis. Because of the complex nature of the system, neural...
Kinetic parameters optimization and modeling of catalytic dehydrogenation of heavy paraffins to Olefins
, Article Petroleum Science and Technology ; Vol. 32, issue. 7 , April , 2014 , pp. 813-820 ; ISSN: 10916466 ; Khorasheh, F ; Nakhjavani, M. H ; Fattahi, M ; Sharif University of Technology
Abstract
A mathematical model for a fixed bed radial flow catalytic reactor was developed for dehydrogenation of heavy paraffins over Pt-Sn/Al2O3 catalyst. The model included appropriate kinetic rate expressions for the main dehydrogenation reaction as well as side reactions and catalyst deactivation. The reactor model consisted of a set of partial and ordinary as well as algebraic equations that were solved numerically to determine the concentration of various species along the radius of the bed as a function of time. The Nelder-Mead optimization method was used to obtain the optimum kinetic parameters. The validity of the model was demonstrated by comparing the predicted paraffin conversion and...
Direct dyes removal using modified magnetic ferrite nanoparticle
, Article Journal of Environmental Health Science and Engineering ; Vol. 12, Issue. 1 , 28 May , 2014 ; ISSN: 2052336X ; Abdi, J ; Bastani, D ; Sharif University of Technology
Abstract
The magnetic adsorbent nanoparticle was modified using cationic surface active agent. Zinc ferrite nanoparticle and cetyl trimethylammonium bromide were used as an adsorbent and a surface active agent, respectively. Dye removal ability of the surface modified nanoparticle as an adsorbent was investigated. Direct Green 6(DG6), Direct Red 31 (DR31) and Direct Red 23 (DR23) were used. The characteristics of the adsorbent were studied using Fourier transform infrared (FTIR), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effect of adsorbent dosage, initial dye concentration and salt was evaluated. In ternary system, dye removal of the adsorbent at 90, 120, 150 and 200 mg/L...